1. Field of the Invention
The present invention relates to a contactless press control device having a self check circuit.
2. Description of the Prior Art
Contactless control devices wherein the relay sequence circuit are replaced by integrated circuits have begun to be used lately as a press control device in order to improve the reliability of the press.
The prior art contactless control device comprises a control circuit to control the press operation and a fault detection circuit to detect and prevent misoperation of the press.
The present invention is directed to further improve the safety of the press operation by adding the function to judge whether or not the fault detection circuit is working. The present invention provides a contactless press control device which is able to discriminate whether or not the fault detecting circuit is functioning normally by applying a dummy signal at the time of power input and when the press has stopped at its top dead center.
According to the present invention, fault detection is performed automatically upon the input of press power and thus, input, fault of the contactless control device is detected before the press start-up. In addition, since fault detection is performed each time the press stops at its top dead center, fault of the control device can be detected before the press operation, making it possible to prevent misoperation of the press. Furthermore since the fault detection time is very short, there is no press operation delay after the press is stopped at its top dead center.
The present invention will now be described in detail with reference to the accompanying drawings in which the presently preferred embodiment of the invention is illustrated by way of example.